Infection by the influenza virus may be more complicated than previously thought. Scientists say the pathogen appears to disarm the immune system’s first responders, which are the first line of defense against disease.

When confronted by the influenza virus, the body’s immune system generates white blood cells that produce antibodies specifically designed to attach to the invading microorganism and neutralize it, preventing infection. These virus-specific cells also retain a memory of the invader so the immune system can fight it in the future if re-exposure occurs.

At least that’s the traditional understanding of how the body fights the flu bug.

Biologists, led by Hidde Ploegh of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, have uncovered how the flu virus can disarm those first responders, known as B cells.

Research with genetically-bred mice suggests the virus gains entry into B cells and disrupts antibody production, a process that ultimately kills the cells and the first line of defense.

If true, Ploegh says the process of infection may be more complicated than previously thought.

“And so we think that this really provides a new window on how the virus goes about its business," he said. "It may have implications in terms of explaining why certain strains of flu cause a nastier version of the disease than others.”

Normally, the frontline antibodies take up residence in lung cells to protect the body against future exposure to microbial invaders through breathing.

The flu virus, however, having disabled the antibodies, may instead target lung cells, thwarting the antibody’s ability to remember the pathogen and launch an immune system attack.

“So this suggests that the initial encounter of the very type of white blood cell that we think defends us against the virus may be taken out by this initial wave of infection,” said Hidde Ploegh.

By disabling the body's so-called 'front line troops', Ploegh says the influenza virus has more time to replicate and gain a foothold before the immune system can mobilize a second wave of defense.

An article on how influenza thwarts the body’s immune response has been published in the journal Nature.